Financial Instruments and Risk Management Financial Instruments and Risk Management (Rollforward of Contingent Consideration) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration	$ 213.2	$ 250.7
Business Combination Contingent Consideration Liability Payments	(82.1)
Business Combination, Contingent Consideration Arrangements, Reclassifications	0.0
Accretion expense	9.0
Fair value loss	35.6
Prepaid expenses and other current assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration	124.8	120.4
Business Combination Contingent Consideration Liability Payments	(82.1)
Business Combination, Contingent Consideration Arrangements, Reclassifications	52.7
Accretion expense	0.0
Fair value loss	33.8
Other long-term obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration	88.4	$ 130.3
Business Combination Contingent Consideration Liability Payments	0.0
Business Combination, Contingent Consideration Arrangements, Reclassifications	(52.7)
Accretion expense	9.0
Fair value loss	$ 1.8